Originally Posted by neuro.psychiatryonline.org

There is significant overlap of the proposed functional circuits and dysfunction at the neurotransmitter level between OCD and schizophrenia, which may lead to co-expression of symptoms. The interactions are multiple and complex, especially in regard to the serotonin and dopamine systems.3 Today controversy centers on whether there is a continuum or overlap in psychopathology between these entities that some authors have called "schizo-obsessive disorder."4 Within this type, several clinically discrete groups were described: OCD patients who become psychotic; schizophrenic patients with comorbid OCD; schizophrenic patients exhibiting OC symptoms; and patients with comorbid OCD and schizotypal personality disorder.5 Existence of these groups may explain the diversity in epidemiological data, clinical manifestations and course, outcomes of various treatments, and prognosis.

OCD in schizophrenic patients, at least in the early stages of the disease, may have a "protective" effect regarding some psychotic symptoms and may be responsible for a less virulent course of illness and a higher level of functioning.6 On the other hand, patients with "OC schizophrenia" tended to have a more chronic course, a greater frequency of social and occupational impairment, and a poor long-term outcome.1,2,6 Treatment with serotonin reuptake blockers, added to the neuroleptic, was found to be efficacious in the treatment of obsessions and compulsions and to improve overall schizophrenic symptoms